PROJECT SUMMARY Anaerobes, bacteria that thrive in the absence of oxygen, are major contributors to both disease and health in humans. While Clostridioides difficile is a serious infectious disease threat and a leading cause of healthcare- associated infections, we are increasingly aware that anaerobes contribute in a beneficial way to the structure and function of the human microbiome. Although regional Societies focused on anaerobe bacterial science have existed in the past in select locales abroad (e.g., Britain, Japan), the Anaerobe Society of the Americas (ASA) is the only continuously active society and the only United States-based Society devoted to the basic and clinical science of anaerobes. Further, the ASA maintains an active international membership, with representation from more than 25 countries at the 2018 Biennial Congress. The long-term goal of the ASA and its biennial congress (founded in 1992) is to promote health and advance science through the study of anaerobic bacteria and their environments. This proposal seeks NIH support for ANAEROBE 2020, the 15th Biennial Congress of the ASA, which will be hosted from July 23-26, 2020 in Seattle, WA. The specific aims of the 15th Biennial Congress are to: (1) stimulate interest in anaerobes among trainees, promote networking among anaerobists from all disciplines, and foster strong mentoring relationships through substantive opportunities for trainee participation including a poster session, early-career investigator awards, and our featured breakout session on publishing led by an editor of the journal Nature; (2) facilitate scientific interchange and demonstrate for trainees how divergent opinions in science are encouraged and discussed via a featured debate; (3) explore the roles of indigenous anaerobes in promoting human health and discuss recent insights into disease induction by anaerobic bacteria including C. difficile and Fusobacteria; (4) accelerate anaerobe research by facilitating methodological advances in culture techniques, genetic manipulation, and model systems; and (5) examine up- to-date clinical management strategies for anaerobic infections and probe emerging mechanisms of action, health benefits, and regulatory issues associated with clinical microbiota transfer. The 15th Biennial Congress will accomplish this goal through presentations by more than 40 domestic and international expert scientific speakers and a variety of presentation formats. In creating the program for ANAEROBE 2020, the Organizing Committee has prioritized diversity and inclusion among participants and attendees. The focused, synergistic program will encourage hearty interdisciplinary exchange between scientists who do not generally congregate in any other conference. Consistent with the goals of the NIH and NIAID, the 15th Biennial Congress of the ASA provides a unique opportunity to bring together the world?s leading basic and clinical investigators in anaerobe bacterial science in order to advance studies with lasting impact on human health.